1. Technical Field
The present invention relates to an optical time division multiplexing circuit, and more particularly to an optical time division multiplexing circuit using a delay interferometer.
2. Related Art
Recently, optical communication technologies are in the limelight as technologies for transmitting a large amount of information at a high speed. Of them, an optical time division multiplexing technology is expected to achieve high-volume and very fast transmission along with wavelength division multiplexing technology.
In optical time division multiplexing technology, an optical time division multiplexing circuit is used. In a conventional optical time division multiplexing circuit, an optical pulse train outputted from a pulse light source is divided into two signals, and the divided signals are respectively inputted to optical modulators for modulation. A specific delay is afforded to one of the modulated optical signals via a delay unit, and then the delayed modulated optical signal is synthesized with the other modulated optical signal to generate a multiplexed optical signal.
In this case, to achieve very fast communication, a phase difference between adjacent pulses must be stabilized by introducing a correct delay into the optical signal. However, since the propagation time of light depends on the influence of environmental temperatures and other factors, it has been difficult to stably introduce a correct delay into an optical signal (for example, refer to JP Patent No. 3508901).